PDFRip
A multi-threaded PDF password cracking utility
...You can write your own queries like STRING{69-420} with the -q option which would generate a wordlist with the full number range. You can pass in an year as the input with the -d option which would bruteforce all 365 days of the year in DDMMYYYY format which is a pretty commonly used password format for PDFs. Just give a number range like 5000-100000 with the -n option and it would bruteforce with the whole range.